1. Field of the Invention
This invention broadly relates to corrosion and scale inhibitors typically used by the oil and gas industries for treatment of their oil and gas wells and transmission lines. More particularly, it is concerned with the discovery that certain relatively critical components and proportions thereof can be employed to prepare a combination corrosion/scale inhibitor composition for use in oil or gas wells which is in the form of a substantially homogeneous dispersion or solution that facilitates use and well coverage of the composition.
2. Description of the Prior Art
It is well known that oil and gas wells are subject to corrosion. Well equipment such as sucker rods, pump rods, tubing, casing and transmission lines are made of mild steel which is adversely affected by the production fluid of the well. The often high temperatures and acidic nature of the fluid magnifies the corrosion problems associated with well equipment.
It is also a well known problem with oil and gas wells that scaling can occur within the well. When scale forms on the well equipment or in the formation it can effectively restrict the flow of fluids thereby resulting in decreased production from the well. Common scale-forming material found in producing fluids includes magnesium sulfate, magnesium carbonate, calcium carbonate, calcium sulfate and barium sulfate.
In order to meet these problems, the oil and gas industries have used various corrosion and scale inhibitors in downhole applications. The corrosion inhibitors are typically aqueous dispersions which may contain a variety of corrosion inhibiting components, e.g., 2-mercaptobenzothiazole, benzotriazole, tolyltriazole, phosphates, polyphosphates, organic soluble polymers, silicates, dithiocarbamates, nitrites, oxazoles, imidazoles, lignins, lignosulfonate, tannins, phosphoric acid esters, and boric acid esters. On the other hand, scale inhibitors such as alkali metal phosphates, alkali metal tripolyphosphates, alkali pyrophosphates have been used in the past.
Generally speaking, use of these types of inhibitors has involved shutting down the well, injecting the inhibitor while running the well pump(s), and in some cases flushing the inhibitors. This is a costly exercise, not only in terms of ingredients, but also down time for the well.
Attempts have been made to ameliorate these problems by combining corrosion and scale inhibitors in a single system. However, the inherent insolubility of many corrosion inhibitors in the aqueous systems of the scale inhibitors has made it impracticable to combine the two components. This problem is especially acute when partial barrel quantities of such a combined inhibitor are used, inasmuch as phase separation between the two inhibitors makes it difficult to obtain the correct proportions in the utilized quantity. As a result, corrosion and scale inhibitors have generally been packaged, sold, handled, stored and used separately even though this practice is a distinct disadvantage from a cost viewpoint.